As in "an echoey room". People do use this word in speech, but it isn't proper in writing. I thought of "echoing", but that implies that something is currently making an echo, whereas what I'm looking for would mean that if there was a noise in the room, it would echo. Are there any real words for this?

I think you'd just have to say "A room with a lot of echo." Most sound engineers would say something like "dead" or possibly "flat" to mean the opposite. An industry person might possibly say something like "bouncy" or the like - but it would be irrelevant to non-arcane usage.
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Joe BlowJul 7 '11 at 12:07

@JoseK: I see. It's just not in dictionary.com. But even here, it's supposed to be used of a sound, not of a room. (Or can I fudge?) And why doesn't this spellchecker allow "echoey"?
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DanielJul 7 '11 at 12:13

Oh well... it doesn't allow "reverberant" either - and I did spell it correctly!
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DanielJul 7 '11 at 12:17

1

@JosefK: echoey has a very clumsy sound though IMO.
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jaybeeJul 7 '11 at 12:21

Edited: though echoing originally meant 'with echoes currently resounding', surely it has an extended meaning as well. "The Queen lives in an echoing palace" doesn't cease to be true when there's no noise.